中国大陆中尺度对流复合体的环境场演变特征

采用合成分析方法,将中国大陆中尺度对流复合体的生命史划分为７ 个子阶段,详细探讨ＭＣＣ演变过程中的能量生消特征。结果表明：在ＭＣＣ的持续阶段,５００ｈＰａ 以下始终有深厚不稳定层存在,不稳定度渐渐减小,水汽、热量从西南和偏南方进入ＭＣＣ,最大通量值出现在９００～５００ ｈＰａ 高度。高、低、中空环流配合对ＭＣＣ的启动和发展有重要意义。     

Bayesian regression model for seasonal forecast of precipitation over Korea

In this paper, we apply three different Bayesian methods to the seasonal forecasting of the precipitation in a region around Korea (32.5°N?C42.5°N, 122.5°E-132.5°E). We focus on the precipitation of summer season (June?CJuly?CAugust; JJA) for the period of 1979?C2007 using the precipitation produced by the Global Data Assimilation and Prediction System (GDAPS) as predictors. Through cross-validation, we demonstrate improvement for seasonal forecast of precipitation in terms of root mean squared error (RMSE) and linear error in probability space score (LEPS). The proposed methods yield RMSE of 1.09 and LEPS of 0.31 between the predicted and observed precipitations, while the prediction using GDAPS output only produces RMSE of 1.20 and LEPS of 0.33 for CPC Merged Analyzed Precipitation (CMAP) data. For station-measured precipitation data, the RMSE and LEPS of the proposed Bayesian methods are 0.53 and 0.29, while GDAPS output is 0.66 and 0.33, respectively. The methods seem to capture the spatial pattern of the observed precipitation. The Bayesian paradigm incorporates the model uncertainty as an integral part of modeling in a natural way. We provide a probabilistic forecast integrating model uncertainty.     

“一带一路”区域气候变化事实、影响及可能风险

“一带一路”区域国家经济、政治发展极不平衡,随着全球气候变暖,区域内的自然环境、气候资源、水资源等都将面临着显著而复杂的变化,并且干旱、洪涝等多种气候灾害是“一带一路”区域可持续发展和重大基础设施建设面临的重大威胁之一。目前,“一带一路”倡议已经进入实质性建设阶段,沿线地区的气候变化及其灾害风险关乎“一带一路”倡议能否顺利实施及亚投行的投资安全。在此背景下,2016—2018年中国科学院地球科学学部实施了“‘一带一路’区域气候变化问题”咨询评议项目,项目针对该区域气候变化的事实、未来变化预估、气候变化的可能影响以及带来的潜在风险等问题进行了系统的调研,并开展了若干分析和研究。经过两年的努力,项目组完成了有关进展报告四份,包括一份总报告和三份分报告。本文扼要地概括和介绍了项目取得的主要成果。     

基于常规气象资料的小时标准冰厚模型及验证

在综合考虑雨凇和雾凇积冰增长以及热力融冰和升华脱冰的基础上,建立了一个基于常规气象资料的小时标准冰厚模型。模拟2008年和2013年浙江省两次严重电网覆冰灾害期间的标准冰厚,并用事故线路调查资料、电线积冰观测站和模拟导线拉力监测点的观测资料进行验证分析。结果显示:事故线路的最大标准冰厚观测值与模拟值相关关系达到0.01显著性水平,电线积冰观测站的日标准冰厚观测值与模拟值的平均绝对偏差小于0.6 mm,模拟导线拉力监测点的小时标准冰厚模拟值与观测值的决定系数为0.8093,均方根误差为0.8 mm。说明模型比较准确地描述了天气过程对电线积冰的影响,能够较好地反映标准冰厚的空间分布规律和时间变化特征。     

用LASGREM降水预报制作黄河三花间面雨量预报

利用ＬＡＳＧＲＥＭ模式输出的降水预报格点数据和ＧｒＡＤＳ系统的气象专用函数,采用客观运行法,研制了黄河三花间面雨量短期预报方法。用该方法计算的“９６”特大暴雨过程三花间区域面雨量与实况接近。     

Future changes in summer precipitation in regional climate simulations over the Korean Peninsula forced by multi-RCP scenarios of HadGEM2-AO

In this study, the regional climate of the Korean Peninsula (KP) was dynamically downscaled using a high-resolution regional climate model (RCM) forced by multi- representative concentration pathways (RCP) scenarios of HadGEM2-AO, and changes in summer precipitation were investigated. Through the evaluation of the present climate, the RCM reasonably reproduced long-term climatology of summer precipitation over the KP, and captured the sub-seasonal evolution of Changma rain-band. In future projections, all RCP experiments using different RCP radiative forcings (i.e., RCP2.6, RCP4.5, RCP6.0, and RCP8.5 runs) simulated an increased summer precipitation over the KP. However, there were some differences in changing rates of summer precipitation among the RCP experiments. Future increases in summer precipitation were affected by future changes in moisture convergence and surface evaporation. Changing ranges in moisture convergences among RCP experiments were significantly larger than those in surface evaporation. This indicates that the uncertainty of changes in summer precipitation is related to the projection of the monsoon circulation, which determines the moisture convergence field through horizontal advection. Changes in the sub-seasonal evolution of Changma rain-band were inconsistent among RCP experiments. However, all experiments showed that Changma rain-band was enhanced during late June to early July, but it was weakened after mid-July due to the expansion of the western North Pacific subtropical high. These results indicate that precipitation intensity related to Changma rain-band will be increased, but its duration will be reduced in the future.     

A mass flux closure function in a GCM based on the Richardson number

A mass flux closure in a general circulation model (GCM) was developed in terms of the mean gradient Richardson number (GRN), which is defined as the ratio between the buoyancy and the shear-driven kinetic energy in the planetary boundary layer. The cloud resolving model (CRM) simulations using the tropical ocean and global atmosphere-coupled ocean–atmosphere response experiment forcing show that cloud-base mass flux is well correlated with the GRN. Using the CRM simulations, a mass flux closure function is formulated as an exponential function of the GRN and it is implemented in the Arakawa–Schubert convective scheme. The GCM simulations with the new mass flux closure are compared to those of the GCM with the conventional mass flux closure based on convective available potential energy. Because of the exponential function, the new closure permits convective precipitation only when the GRN has a sufficiently large value. When the GRN has a relatively small value, the convection is suppressed while the convective instability is released by large-scale precipitation. As a result, the ratio of convective precipitation to total precipitation is reduced and there is an increase in the frequency of heavy precipitation, more similar to the observations. The new closure also improves the diurnal cycle of precipitation due to a time delay of the large GRN with respect to convective instability.     

全球平均经圈环流的基本特征及其与臭氧关系研究

本文利用1957年9月到2002年8月,共540个月的ERA-40的经向风和臭氧质量混合比月平均资料,分析研究了平均经圈环流(MMC)和Hadley环流强弱特征变化及其与臭氧变化的关系.分析指出:(1)平均经圈环流与臭氧分布在垂直方向上有很好的对应和相关关系,平均经圈环流是形成臭氧水平、垂直的气候平均态分布,季节变化,年代际变化的重要因素;(2)垂直方向上北半球臭氧浓度的变化比南半球的变化更明显;(3)典型相关分析表明平均经圈环流与臭氧浓度变化在不同的高度和纬度上有不同的相关关系,臭氧与Hadley和Ferrel环流存在密切的相关关系,特别是Hadley环流,这表明Hadley环流在全球大气臭氧的变化中起重要作用.     

基于变分原理的自适应网络技术及其权函数问题研究

利用两个具有解析解的算例研究基于变分原理的自适应网络技术。结果表明，对运动激波算例，权函数考虑二阶导数项比考虑梯度项更能有效地减小误差；对气旋锋生算例，仅以梯度作为权函数亦不能提高精度，考虑速度场、锋生函数分布的权函数能更合理地安排网络；对照解析解，发现提出的自适应网络技术能明显提高计算精度，在节省内存等方面显示了突出的优点。     

郑州市年降水的奇异谱分析

运用奇异谱分析方法对郑州市19512006年的年降水资料进行分析,结果表明:郑州市近56 a来的年降水趋势变化不太显著,主要以波动变化为主,存在9、7、5、3 a的振荡周期,各振荡周期存在年代际变化,不同阶段各周期强弱表现不同.